In the Laser Centre of the Institute of Physical
Chemistry of the Polish Academy of Sciences and the Faculty of Physics of the
Warsaw University work has started on the construction of an innovative laser.
The compact device will make use of a unique light amplification technology to
allow single laser pulses to reach the power of tens of terawatts with world
record-breaking amplification parameters.

Most lasers amplify
light by making use of classical technology with titanium ions doped sapphire
crystals. An external laser is used to pump energy into the crystal where a
part of the energy is subsequently taken over by a laser beam being amplified.
Laser crystals have, however, numerous disadvantages, e.g., they warm up
strongly and distort the cross section of the laser beam. An alternative is
provided by parametric amplifiers that exploit non-linear optical effects. A
laser with such an amplifier is being developed in the Laser Centre at the Institute of Physical Chemistry of the
Polish Academy of Sciences (IPC PAS) and the Faculty of Physics of the Warsaw
University (FPWU). "Our goal is simple. We want to construct the most
efficient and compact parametric amplifier in the world" - says Dr Yuriy
Stepanenko from IPC PAS.

The multi-pass optical
parametric amplifier technology NOPCPA (Noncollinear Optical Parametric Chirped
Pulse Amplifier) has been for several years developed in the Laser Centre in a
group headed by Prof. Czesław Radzewicz (IPC
PAS, FPWU). The method
consists in an efficient energy transfer directly from the pumping laser beam
to the beam being amplified. Combined with numerical modelling, theoretical
tools developed by Polish researchers allow to optimize precisely the
parameters of both beams and of the amplifier. These issues are non-trivial as
field intensity distributions are inhomogeneous in time and space, and in
addition the pulse being amplified has a time-dependent frequency (which the
physicists call a chirp).

As no energy is being
accumulated in a parametric amplifier, there are no damaging thermal effects,
and the amplified pulses have excellent parameters. A NOPCPA amplifier has also
compact dimensions: a length of several centimetres is enough to reach an
amplification of hundreds of millions of times. Theoretical efficiency of such
an amplifier is approximately 60% but it is difficult to get, and so far the
best laser amplifier of this type reach below 30%. "Our minimum plan is to
reach an efficiency of 40%, we will try, however, to overcome a barrier of 50%"
- says Dr Paweł Wnuk (IPC PAS).

The researchers expect
to get the first 10 terawatt pulses with duration of dozen femtoseconds emitted
by their laser next year. But this is only the beginning of the way. "We hope
that already the present version of the parametric amplifier will allow us to
generate over 100 TW pulses" - stresses Prof. Radzewicz. The calculations indicate
that 500 TW laser pulses could be used to accelerate protons to energies
enabling them to be applied in medical therapies including anti-cancer
treatment. The lasers with so high power can be found today only in a few
research centres worldwide. "We have all the grounds to assume that our method
of light amplification can in future help us to build relatively cheap lasers
for proton acceleration, in addition with so compact size that they essentially
would be considered portable devices" - says Dr Stepanenko.

Under the research
project being completed the new laser will be used to construct two
demonstration setups. The first one, being developed in collaboration with the
Military Academy of Technology (MAT) in Warsaw and the Institute of Physics of
the PAS, will be used to construct x-ray sources with micrometric dimensions.
Such sources are used in, e.g., x-ray microscopy, and in particular in
non-destructive testing of structural materials. The second demonstrator will
be a lidar for measurements of atmospheric pollution and will be developed with
participation of the researchers from the Military Academy of Technology.

The Institute of Physical
Chemistry of the Polish Academy of Sciences (http://www.ichf.edu.pl/) was established in 1955
as one of the first chemical institutes of the PAS. The Institute's scientific
profile is strongly related to the newest global trends in the development of
physical chemistry and chemical physics. Scientific research is conducted in
nine scientific departments. CHEMIPAN R&D Laboratories, operating as part
of the Institute, implement, produce and commercialise specialist chemicals to
be used, in particular, in agriculture and pharmaceutical industry. The
Institute publishes approximately 200 original research papers annually.